Angry Birds has already received several expansion packs on Android and iOS. The rising popularity of the franchise has also prompted Rovio Mobile and 20th Century Fox to join forces to create an animated feature film, called Rio, that’s due to hit theaters this Spring. Now, it appears Rovio will be adding more depth to their hit game.

In a recent chat with the good folks at Pocket-Lint, Rovio confirmed that a 3D version of Angry Birds is in the works. “We’ve built a lot of 3D games before, it’s not like it’s a lot of learning in order to recreate the technology with Angry Birds,” said Rovio’s Peter Vesterbacka. We assume they’re referring to a bump from traditional 2D to virtual 3D graphics, and not the simulated 3D that’s being shown off at MWC on devices like the Optimus 3D. In 2006, Rovio acquired Pixelgene, developers of 3D mobile games, so they certainly have the resources to enhance the graphics of their games. Devices and platforms for the 3D variant were not specified.

Rovio also discussed the progress of Angry Birds for Windows Phone 7. If you haven’t heard, WP7 gamers are still waiting, not for an update, but for a port of the original game to hit their platform of choice.

If you recall, the longer than expected wait spurred one irritated WP7 developer to create an Angry Birds clone, called Chicks’n’Vixens. The indie game developer even suggested that Rovio has been slacking by boldly saying they “should be able to do better.” Well, Rovio explained the reasoning behind the wait.

It turns out, all eyes should be on Microsoft. “Let’s just say, Microsoft has a lot of lawyers,” said Vesterbacka. We also noticed that Rovio responded with a similar statement when one of our readers forwarded our post on Chicks’n’Vixens to them via Twitter. The Finnish game developer said: it has “nothing to do with slacking. All to do with contracts. Development wouldn’t take long at all.”

So, there you have it, Rovio is still actively working on bringing Angry Birds to Windows Phone 7, and a 3D version will be coming as well. If you’re a WP7 user, has interest in the game dwindled because of the delay? Will the transition to 3D make the game more or less enjoyable? Hit us up in the comments below.